DC1896A - Demo Manual

DEMO CIRCUIT 1896A
LTC3633AEFE-3
DEMO BOARD
MANUAL
DESCRIPTION
LTC3633AEFE-3
DUAL CHANNEL 3A 20V MONOLITHIC
SYNCHRONOUS STEP-DOWN REGULATOR
BOARD
Demonstration circuit DC1896 is a dual output regulator
consisting of two constant-frequency step-down converters, based on the LTC3633A-3 monolithic dual channel
synchronous buck regulator. The DC1896 has an input
voltage range of 3.6V to 20V, with each regulator capable
of delivering up to 3A of output current. The DC1896 can
operate in either Burst Mode or forced continuous
mode. In shutdown, the DC1896 can run off of less than
15 uA total. The DC1896 is a very efficient circuit: up to
90%. The DC1896 uses the 28 Pin QFN LTC3633AEFE-3
package, which has an exposed pad on the bottom-side
of the IC for better thermal performance. These features,
plus a programmable operating frequency range from
500 kHz to 4 MHz (2 MHz switching frequency with the
RT pin connected to INTVcc), make the DC1896 demo
board an ideal circuit for use industrial or distributed
power applications. Design files for this circuit are
available at www.linear.com/demo.
QUICK START PROCEDURE
The DC1896 is easy to set up to evaluate the
performance of the LTC3633A-3. For a proper
measurement equipment configuration, set up
the circuit according to the diagram in Figure
1.
NOTE: When measuring the input or output
voltage ripple, care must be taken to avoid a
long ground lead on the oscilloscope probe.
Measure the input or output voltage ripple by
touching the probe tip directly across the Vin
or Vout and GND terminals. See the proper
scope probe technique in figure 2.
soft-start (SS) positions of headers JP3 and
JP4, shunt XJP8 into the forced continuous
mode (FCM) position of MODE header JP8,
shunt XJP14 into the 1 MHz position of the
frequency (FREQ) header JP14, shunts
XJP12 and XJP13 into the external (EXT)
compensation positions of headers JP12 and
JP13, and shunt XJP6 into the Vout1 voltage
options of choice of header JP6: 1.5V, 1.8V, or
2.5V, and a shunt into the Vout2 voltage option
of choice: 2.5V (header JP15), 3.3V (header
JP5), or 5V (header JP7).
Please follow the procedure outlined below for
proper operation.
1. Connect the input power supply to the
Vin1/Vin2 and GND terminals (Vin1 and Vin2
are separate nodes.). Connect the loads between the Vout and GND terminals. Refer to
figure 1 for the proper measurement equipment setup.
2. Apply 5.5V at Vins 1 & 2. Measure both
Vouts; they should read 0V. If desired, one
can measure the shutdown supply current at
this point. The supply current will be less than
15 uA in shutdown.
Before proceeding to operation, insert jumper
shunts XJP1 and XJP2 into the OFF positions
of headers JP1 and JP2, shunt XJP11 into the
ON position (180°out-of-phase) of PHASE
header JP11, shunts XJP3 and XJP4 into the
3. Turn on Vout1 and Vout2 by shifting shunts
XJP1 and XJP2 from the OFF positions to the
ON positions. Both output voltages should be
within a tolerance of +/- 2%.
4. Vary the input voltages from 5.8V (the min.
Vin is dependent on Vout) to 20V, and the load
currents from 0 to 3A. Both output voltages
should be within +/- 3% tolerance.
1
LTC3633AEFE-3
5. Set the load current of both outputs to 3A and the input voltages to 20V, and then measure each output ripple voltage
(refer to figure 2 for proper measurement technique); they should each measure less than 30 mVAC. Also, observe the
voltage waveform at either switch node (pins 23 & 24 for reg.1 and 13 & 14 for reg.2) of each regulator. The switching
frequencies should be between 800 kHz and 1.2 MHz (T = 1.25 us and 0.833 us). To attain 2 MHz operation, change the
shunt position on header JP14. In all cases, both switch node waveforms should be rectangular in shape, and 180outof-phase with each other. Change the shunt position on header JP11 to set the switch waveforms in phase with respect to
each other. To operate the ckt.s in Burst Mode, change the shunt in header JP8 to the Burst Mode position. When
finished, insert shunts XJP1 and XJP2 to the OFF position(s) and disconnect the power.
6. Regulators 1 (VIN1) and 2 (VIN2) are completely separated from each other; thus, they can be powered from different individual input supplies, as can the signal input supply. Of course, all the voltage requirements still must be met: 1.5V to 20V for the
PVin pins and 3.6V to 20V for the SVin pin.
Warning - If the power for the demo board is carried in long leads, the input voltage at the part could “ring”, which could affect the
operation of the circuit or even exceed the maximum voltage rating of the IC. To eliminate the ringing, a small tantalum capacitor (for
instance, AVX part # TPSY226M035R0200) is inserted on the pads between the input power and return terminals on the bottom of the
demo board. The (greater) ESR of the tantalum capacitor will dampen the (possible) ringing voltage caused by the long input leads.
On a normal, typical PCB, with short traces, this capacitor is not needed.
Table 1. Performance Summary (TA = 25°C)
PARAMETER
CONDITIONS
VALUE
Minimum Input Voltages
3.6V
Maximum Input Voltages
20V
RUN Pin = GND
Shutdown
RUN Pin = VIN
Operating
Output Voltage VOUT1 Regulation
VIN1 = 3.6V to 20V, IOUT1 = 0A to 3A
1.5V ±3% (1.455V - 1.545V)
1.8V ±3% (1.746V – 1.854V)
2.5V ±3% (2.425V – 2.575V)
Typical Output Ripple VOUT1
VIN1 = 12V, IOUT1 = 3A (20 MHz BW)
< 30mVP–P
Output Voltage VOUT2 Regulation
VIN2 = 3.6V to 20V, IOUT2 = 0A to 3A
2.5V ±3% (2.425V – 2.575V)
3.3V ±3% (3.201V – 3.399V)
5V ±3% (4.85V – 5.15V)
Typical Output Ripple VOUT2
VIN2 = 12V, IOUT2 = 3A (20 MHz BW)
< 30mVP–P
RT Pin connected to 324k
RT Pin = INTVCC
Channel 1: Vin = 12V, Vout1 = 1.8V, Fsw = 1 MHz
Channel 2: Vin = 12V, Vout2 = 3.3V, Fsw = 1 MHz
Channel 1: Vin = 12V, Vout1 = 1.8V, Fsw = 2 MHz
Channel 2: Vin = 12V, Vout2 = 3.3V, Fsw = 2 MHz
Phase Pin = INTVCC
Phase Pin = GND
1 MHz
2 MHz
Iout1 < 1.5A
Iout2 < 1.25A
Iout1 < 1A
Iout2 < 0.75 A
Out-of-Phase
In Phase
3.3V ±6%
Run
Nominal Switching Frequencies
Burst Mode Operation
Output Current Thresholds
Phase
INTVCC
2
LTC3633AEFE-3
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
3
LTC3633AEFE-3
Figure 3. LTC3633A-3 DC1896 Switch Operation
VIN1&2 = 12V, VOUT1 = 1.8V @ IOUT1 = 3A, VOUT2 = 3.3V @ IOUT2 = 3A
Forced Continuous Mode FSW = 1 MHz
External Compensation: Rithx = 13k, Cithx = 220 pF
Trace 1: VSW1 (10V/div)
Trace 3: VOUT1 AC Voltage (20mV/div AC)
Trace 2: VSW2 (10V/div)
Trace 4: VOUT2 AC Voltage (20mV/div AC)
4
LTC3633AEFE-3
Figure 4. VOUT1 Load Step Response
VIN1 = 12V, VOUT1 = 1.8V, 3A Load Step (0A <-> 3A)
Forced Continuous Mode FSW = 1 MHz
External Compensation: Rith1 = 13k, Cith1 = 220 pF
Trace 1: Output Voltage (100mV/div AC)
Trace 4: Output Current (1A/div)
5
LTC3633AEFE-3
Figure 5. VOUT2 Load Step Response
VIN2 = 12V, VOUT2 = 3.3V, 3A Load Step (0A <-> 3A)
Forced Continuous Mode FSW = 1 MHz
External Compensation: Rith2 = 13k, Cith2 = 220 pF
Trace 1: Output Voltage (200mV/div AC)
Trace 4: Output Current (1A/div)
6
LTC3633AEFE-3
Figure 6. LTC3633A-3 DC1896 Efficiency
7
E2
E15
E6
E4
E1
E16
[1]
+ CIN6
22uF
25V
7343
22uF
25V
7343
+ CIN5
[1]
COUT3
22uF
6.3V
1206
5
6
CIN4
22uF
25V
1210
OPT
2.5V
1.8V
CIN2
22uF
25V
1210
VIN2
1%
R12
OPT
VIN1
INT
EXT
OPT
D1
3
2
1
2MHz
(INT.)
1MHz
JP12
ITH1
C1
0.1uF
RUN1
R1 1M
JP3
26
27
22
JP14
U1
LTC3633AEFE-3
14
12
15
17
16
20
23
9
3
2
1
CC2
10pF
OPT
INTVCC
220pF
CITH2
RITH2
13K
1%
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
6
4
JP13
ITH2
INT
EXT
5
3
1
R8 11.5K 1%
R6 18.7K 1%
R10 26.7K 1%
VOUT2
5V
3.3V
2.5V
JP7
JP5
SCALE = NONE
DATE:
N/A
SIZE
GND
GND
TECHNOLOGY
R11
10k
SYNC
LTC3633AEFE-3
DEMO CIRCUIT 1896A
05/03/13 12:32:05
IC NO.
SHEET 1
OF 1
1
REV.
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900 www.linear.com
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
E12
VO2 SELECT
E14
E7
VOUT2
SVIN
GND
PGOOD2
TRACK2
DUAL SYNCHRONOUS STEP-DOWN
REGULATOR
TITLE: SCHEMATIC
E13
E3
E8
E11
CSVIN1
1uF
E5
COUT6
10uF
6.3V
0805
JP15
COUT4
22uF
6.3V
1206
VIN2
FCM (FORCED CONTINUOUS MODE)
APP ENG. TOM G.
PCB DES. MI
D4
RTR4
OPT
RTR2 0
CMDSH-3-TR
COUT2
22uF
6.3V
1206
CSVIN
1uF
BURST MODE
SYNC
APPROVALS
JP8
MODE
3
2
1
R4
84.5K
1%
D3
SVIN
CMDSH-3-TR
INTVCC
VIN1
INTVCC
OPT
D2
CFFW2
10pF
JP2
OFF
ON
TRACK
SS
SVIN RUN2
JP4
C2
0.1uF L2 2.2uH
VISHAY
IHLP-2020BZER2R2M01
RUN2
R2 1M
CUSTOMER NOTICE
ITH2
VFB2
VON2
SW2
SW2
BOOST2
SVIN
RUN2
RPG2
100K
3
2
1
TRACK/SS2
3
RT
324K
1%
220pF
CITH1
ITH1
VFB1
VON1
SW1
SW1
BOOST1
PHMODE
RUN1
VIN2
CTR2
4700pF
2
INTVCC
INTVCC
RITH1
13K
1%
1
3
28
VIN1
1uF
CVCC
CVCC1 1uF
INTVCC
2
1
FREQ
CC1
10pF
OPT
5
6
RPG1
100K
VISHAY
IHLP-2020BZER1R0M01
L1 1.0uH
JP1
3
2
1
CFFW1
10pF
OFF
ON
RUN1 SVIN
TRACK
3
2
CTR1
4700pF
[1] CIN5 AND CIN6 ARE INSERTED ON DC1896A TO DAMPEN THE (POSSIBLE) RINGING VOLTAGE DUE
TO THE USE OF LONG INPUT LEADS. ON A NORMAL, TYPICAL PCB, WITH SHORT TRACES,
CIN5 AND CIN6 ARE NOT NEEDED.
R9 11K
R7 17.4K 1%
R3
34.8K
1%
R5 23.2K 1%
COUT1
22uF
6.3V
1206
INTVCC
RPHMDE 1M
INTVCC
1.5V
CIN1
22uF
25V
1210
VIN1
VIN2
CIN3
22uF
25V
1210
OPT
3
4
JP6
1
2
VO1 SELECT
COUT5
10uF
6.3V
0805
VOUT1
JP11
3
2
1
PHASE
OFF
ON
RTR3
OPT
RTR1 0
NOTES: UNLESS OTHERWISE SPECIFIED,
V02 - V6.3
VIN2
V 02 - V 6. 3
VIN1
GND
GND
3A
VOUT1
PGOOD1
TRACK1
E9
SS
1
TRACK/SS1
25
24
PVIN1
PVIN1
4
PGOOD1
INTVCC
SGND
10
PGND
29
RT
8
2
TRACK/SS1
21
INTVcc
13
TRACK/SS2
11
PGOOD2
18
19
PVIN2
PVIN2
MODE/SYNC
7
A3
8
E10
LTC3633AEFE-3
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